Deep in the Atlantic Ocean, sea explorers and divers discovered unexplored areas with a pattern of holes in the sand. On July 23, they saw a ton of holes creating lines on the ocean floors. A week later, there were more holes on the Azores Plateau. Those holes were a mile deep, but all the scientists didn’t know what the holes were. Fortunately, they discovered similar markings called “lebensspuren,” which means “life traces” in German.

Many scientists who study the ocean wonder: “What is creating those marks, with the holes spaced 4 or more inches apart and the lines extending from 5 feet to more than 6 feet, on the ocean floor?” They say the holes look human-made, though. But a long time later, they still haven’t found out what the holes are. Experts with NOAA (National Oceanic and Atmospheric Administration) are planning voyages. They are paying close attention to coral and sea sponges, which are “some of the most valuable marine ecosystems on Earth,” according to the New York Times.

Scientists who study the ocean get conspiracies: Are the holes man-made? Could they be a sign from extraterrestrials? Are they tracks left by a submarine? Could they be the breathing holes of a “deep-sea creature that buries itself under the sand?”